Cold formed laminates

ABSTRACT

The principles and embodiments of the present disclosure relate generally to complexly curved laminates made from a complexly curved substrate and a flat substrate, such as automotive window glazings, and methods of cold forming complexly-curved glass products from a curved substrate and a flat substrate. In one or more embodiments, the laminate includes first complexly-curved glass substrate with a first surface and a second surface opposite the first surface, a second complexly-curved glass substrate with a third surface and a fourth surface opposite the third surface with a thickness therebetween; and a polymer interlayer affixed to the second convex surface and third surface, wherein the third surface and fourth surface have compressive stress values respectively that differ such that the fourth surface has as compressive stress value that is greater than the compressive stress value of the third surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/068,380, filed on Nov. 10, 2020, which is a continuation of U.S.application Ser. No. 16/002,160, filed on Jun. 7, 2018 and claims thebenefit of priority under 35 U.S.C. § 119 of U.S. application Ser. No.15/204,452, filed on Jul. 7, 2016 which, claims the benefit of priorityunder 35 U.S.C. § 119 of U.S. Provisional Application Ser. No.62/339,145 filed on May 20, 2016, U.S. Provisional Application Ser. No.62/281,301 filed on Jan. 21, 2016 and U.S. Provisional Application Ser.No. 62/190,828 filed on Jul. 10, 2015, the contents of which are reliedupon and incorporated herein by reference in their entirety.

TECHNICAL FIELD

Principles and embodiments of the present disclosure relate generally tocold-formed complexly curved laminates and methods of cold-forming suchlaminates.

BACKGROUND

Curved laminates are used in a variety of applications includingautomotive glazing and architectural windows. For such applications,sheets of glass are precisely bent to defined shapes and/or curvaturesdetermined by the configurations and sizes of the openings, as well asthe vehicle style or architectural aesthetics. Such curved laminates maybe made by heating flat glass sheets to a suitable temperature forforming, applying forces to the sheet to change the shape, thenlaminating two curved sheets together. This process is typicallyreferred to as a “hot bending” process. In some known examples, theglass may be heated in a furnace and formed while the sheet is still ina high temperature state (at or near the softening temperature of theglass) within the furnace. Glass sheets may also be bent by initiallyheating the glass sheet in a furnace to a suitable temperature at ornear the softening temperature of the glass, then transferring the glasssheet to a glass bending apparatus outside the furnace. Glass sheetsthat undergo such bending operations typically have been 2.5 mm, 3 mm,or greater in thickness.

Curved laminates typically must meet stringent optical requirements, andthe viewing area of the closures or windows must be free of surfacedefects and optical distortion that can interfere with the clear viewingthrough the curved laminate. Glass that is not at an appropriatetemperature during a bending operation may exhibit optical distortions,such as roller waves (optical roll distortion) and/or discretemarking(s) and/or defect(s) that may make the bent sheet unsuitable forits intended purpose.

Presently existing methods to form complexly curved laminates presentlyrequire heating and bending two glass sheets at or near the softeningpoint of the glass to form a single laminate, and/or typically use verythick glass sheets to facilitate bending operations leading to greateroverall weight of the laminate. Moreover, when two glass sheets requirediffering forming conditions or processes (e.g., due to differingsoftening points and/or thicknesses), the two glass sheets are typicallyformed separately and then joined, often leading to shape mismatch andunnecessary processing steps and cost. Accordingly, such methods requirecomplex manufacturing processes incurring longer manufacturing time andmore cost.

Automotive glazing and architectural applications are increasinglydemanding complexly curved laminates, which are thinner than currentlyavailable laminates. Accordingly, there is a need for such laminatesthat can be shaped and laminated using fewer processing steps and havingmore precise shape matching.

SUMMARY

A first aspect of this disclosure relates to laminates having complexlycurved shapes. In one or more embodiments, the laminates are cold-formedby laminating a flat substrate to a curved substrate. As used herein,“cold-forming” refers to a laminate forming process that is performed attemperature well below the softening temperature of either of thesubstrates. According to one or more embodiments, the laminate iscold-formed at a temperature at least 200° C. below the softeningtemperature of either of the substrates. In some embodiments, thecold-formed, complexly curved laminates include a thin substrate (e.g.,having a thickness less than about 1 mm), which results in a laminatethat has reduced weight. The laminates described herein according to oneor more embodiment, exhibit a desirable complexly curved shape, withoutoptical defects and distortions that are often found in known, complexlycurved laminates (which are typically formed using a hot bendingprocess).

In one embodiment, a laminate comprises: a first complexly-curved glasssubstrate having a first surface, a second surface opposite the firstsurface, and a first thickness therebetween; a second complexly-curvedglass substrate having a third surface, a fourth surface opposite thethird surface, and a second thickness therebetween; and a polymerinterlayer affixed to the second surface and third surface.

In one or more embodiments, either one or both the firstcomplexly-curved glass substrate and the second complexly-curved glasssubstrate has a thickness in the range of about 0.1 mm to about 1 mm orfrom about 0.2 mm to about 0.7 mm. In particular, in one or moreembodiments, the second complexly curved glass substrate has atthickness less than the first complexly curved glass substrate. In oneor more embodiments, the third and fourth surfaces respectively havecompressive stress values such that the fourth surface has a compressivestress value that is greater than the compressive stress value of thethird surface. In one or more embodiments, the first and third surfacesform convex surfaces while the second and fourth surfaces form concavesurfaces.

Another aspect of this disclosure pertains to a method for forminglaminates. In one embodiment, a method of producing a complexly-curvedlaminate, comprises: placing a bonding layer between a complexly curvedsubstrate and a flat, strengthened glass substrate to form a stack;applying pressure to the stack to press the strengthened glass substrateagainst the bonding layer which is pressed against the complexly curvedsubstrate; and heating the complexly curved substrate, bonding layer,and complexly curved strengthened glass substrate to a temperature below400° C. to form a complexly-curved laminate in which the strengthenedglass substrate conforms in shape to the complexly curved substrate.

The methods described herein do not require heating and bending of bothsubstrates, thus reducing manufacturing time and cost by avoidingheating and bending operations for both of the substrates. In one ormore embodiments, the method includes strengthening one substratechemically, thermally, mechanically or a combination thereof.

In another embodiment, a method of producing a complexly-curvedlaminate, comprises: forming a first glass substrate having two majorsurfaces and a thickness therebetween to have a curvature along two axesand to provide a complexly curved glass substrate; arranging thecomplexly curved glass substrate with a bonding layer and a second glasssubstrate in a stack such that the bonding layer is between thecomplexly curved glass substrate and the second glass substrate. In oneor more embodiments, the second glass substrate has two major surfacesand a thickness therebetween to have a curvature along two axes, whereinthe curvature of the second glass substrate does not match the curvatureof the first glass substrate. In one or more embodiments, the methodincludes applying pressure to the stack at room temperature to shape thesecond glass substrate to conform to the curvature of the complexlycurved glass substrate to form a complexly curved laminate.

Additional features will be set forth in the detailed description whichfollows, and in part will be readily apparent to those skilled in theart from that description or recognized by practicing the embodiments asdescribed herein, including the detailed description which follows, theclaims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of an exemplary embodiment ofa laminate;

FIG. 2 illustrates a cross-sectional view of an exemplary embodiment ofa flat glass substrate, a curved glass substrate and an intervening filmlayer before shaping; and

FIG. 3 is a graph showing laminate shape for a laminate according anembodiment of the disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiment, examples ofwhich are illustrated in the accompanying drawings.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “various embodiments,” “one or more embodiments” or “anembodiment” means that a particular feature, structure, material, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the disclosure. Thus, the appearances ofthe phrases such as “in one or more embodiments,” “in certainembodiments,” “in various embodiments,” “in one embodiment” or “in anembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Automotive and architectural applications often require light-weight yetmechanically strong laminates for various uses. In the automotive field,there is a need to reduce the weight of vehicles to thereby improve fuelefficiency. One approach to reduce the weight of vehicles is to reducethe thickness of laminates and/or substrates used in laminates. There isalso a need for laminates with increasingly complexly curved shapesmeeting aesthetic requirements. For example, in the automotive field,windshields, backlights, sun-roofs, fix-mounted roof panels, andsidelights are utilizing laminates with complexly curved shapes. Inarchitecture, such complexly curved laminates may be used in variousexterior and interior applications (e.g., walls, countertops,appliances, modular furniture, etc.).

The bending requirements of inorganic materials often limit thethickness of the plies used in curved laminates. It has been found thatthin glass substrates having a thickness of about 1.5 or 1.4 mm or lesscan cool too quickly to be curved and formed properly using known hotbending methods, which can result in unacceptable flaws or the laminatebreaking during the hot bending operation. In addition, thin glasssubstrates having a thickness of about 1.5 mm or less can be more proneto distortion if heated to higher temperatures to off-set such cooling.The leading and trailing edges of each glass substrate form a cantileverwhen the substrate edge is unsupported by a roller bending apparatus.When heated above a particular temperature, a glass substrate(regardless of thickness) can sag under the load of its own cantileveredweight; however such sagging can be greater for thinner substrates andsubstrates heated to higher temperatures. Such sagging may also occuracross the unsupported sections of a substrate between support rollers.One or more of these problems may be addressed by the variousembodiments described herein.

A first aspect of the present disclosure is related to a cold-formedlaminate having a complexly curved shape. In one or more embodiments,the laminate may be obtained from a first substrate having a complexlycurved shape and a second substrate having a flat or planar shape. Asused herein, “flat” and “planar” are used interchangeably and mean ashape having curvature less than a curvature at which lamination defectsare created due to curvature mismatch, when such a flat substrate iscold-formed to another substrate (i.e., a radius of curvature of greaterthan or equal to about 3 meters, greater than or equal to about 4 metersor greater than or equal to about 5 meters) or a curvature (of anyvalue) along only one axis. A flat substrate has the foregoing shapewhen placed on a surface. As used herein “complex curve” and “complexlycurved” mean a non-planar shape having curvature along two orthogonalaxes that are different from one another. Examples of complexly curvedshapes includes having simple or compound curves, also referred to asnon-developable shapes, which include but are not limited to spherical,aspherical, and toroidal. The complexly curved laminates according toembodiments may also include segments or portions of such surfaces, orbe comprised of a combination of such curves and surfaces. In one ormore embodiments, a laminate may have a compound curve including a majorradius and a cross curvature. A complexly curved laminate according toembodiments may have a distinct radius of curvature in two independentdirections. According to one or more embodiments, complexly curvedlaminates may thus be characterized as having “cross curvature,” wherethe laminate is curved along an axis (i.e., a first axis) that isparallel to a given dimension and also curved along an axis (i.e., asecond axis) that is perpendicular to the same dimension. The curvatureof the laminate can be even more complex when a significant minimumradius is combined with a significant cross curvature, and/or depth ofbend. Some laminates may also include bending along axes that are notperpendicular to one another. As a non-limiting example, thecomplexly-curved laminate may have length and width dimensions of 0.5 mby 1.0 m and a radius of curvature of 2 to 2.5 m along the minor axis,and a radius of curvature of 4 to 5 m along the major axis. In one ormore embodiments, the complexly-curved laminate may have a radius ofcurvature of 5 m or less along at least one axis. In one or moreembodiments, the complexly-curved laminate may have a radius ofcurvature of 5 m or less along at least a first axis and along thesecond axis that is perpendicular to the first axis. In one or moreembodiments, the complexly-curved laminate may have a radius ofcurvature of 5 m or less along at least a first axis and along thesecond axis that is not perpendicular to the first axis.

FIG. 1 illustrates one embodiment of a laminate 100 including a firstsubstrate 110 having a complexly curved shape and having at least oneconvex surface provided by a first surface 112 opposite at least oneconcave surface provided by a second surface 114 with a thicknesstherebetween. The laminate also includes a second substrate 130 that hasbeen cold-formed and is complexly-curved. The second substrate 130includes at least one convex surface provided by a third surface 132opposite at least one concave surface provided by a fourth surface 134,with a thickness therebetween. As shown in FIG. 1, an interlayer 120 maybe disposed between the first substrate 110 and the second substrate130. In one or more embodiments, the interlayer 120 is affixed to atleast second surface 114 and the third surface 132 of the laminate. Asused herein, the term “convex surface” means outwardly bending orcurving as shown in FIG. 1 at reference numbers 112 and 132. The term“concave surface” means inwardly bending or curving as shown in FIG. 1at reference numbers 114, 134.

In one or more embodiments, prior to the cold-forming process, therespective compressive stresses in the third surface 132 and fourthsurface 134 are substantially equal. In embodiments in which the secondsubstrate 130 is unstrengthened (as defined herein), the third surface132 and the fourth surface 134 exhibit no appreciable compressivestress, prior to cold-forming. In embodiments in which the secondsubstrate 130 is strengthened (as described herein), the third surface132 and the fourth surface 134 exhibit equal compressive stress withrespect to one another, prior to cold-forming. In one or moreembodiments, after cold-forming, the compressive stress on the fourthsurface 134 increases (i.e., the compressive stress on the fourthsurface 134 is greater after cold-forming than before cold-forming).Without being bound by theory, the cold-forming process increases thecompressive stress of the substrate being shaped (i.e., the secondsubstrate) to compensate for tensile stresses imparted during bendingand/or forming operations. In one or more embodiments, the cold-formingprocess causes the third surface of that substrate (i.e., the thirdsurface 132) to experience tensile stresses, while the fourth surface ofthe substrate (i.e., the fourth surface 134) experiences compressivestresses.

When a strengthened second substrate 130 is utilized, the third andfourth surfaces (132, 134) of the second substrate are already undercompressive stress, and thus the third surface 132 can experiencegreater tensile stress. This allows for the strengthened secondsubstrate to conform to more tightly curved surfaces. Thus, for thelaminate shown in FIG. 1, after forming of the laminate 100, the thirdsurface 132 has a compressive stress that is less than the compressivestress of the fourth surface 134. In other words, the fourth surface 134compressive stress is greater than the third surface 132 compressivestress.

In one or more embodiments, the increased compressive stress in thefourth surface 134 (relative to the third surface) provides greaterstrength to the fourth surface 134, which is an exposed surface afterthe laminate has been formed.

In one or more embodiments, the second substrate 130 has a thicknessless than the first substrate 110. This thickness differential means thesecond substrate 130 may exert less force and is more flexible toconform to the shape of the first substrate 110. Moreover, a thinnersecond substrate 130 may deform more readily to compensate for shapemismatches and gaps created by the shape of the first substrate 110. Inone or more embodiments, a thin and strengthened second substrateexhibits greater flexibility especially during cold-forming.

In one or more embodiments, the second substrate 130 conforms to thefirst substrate 110 to provide a substantially uniform distance betweenthe second surface 114 and the third surface 132, which is filled by theinterlayer.

In one or more embodiments, the laminate 100 may have a thickness of6.85 mm or less, or 5.85 mm or less, where the thickness of the laminate100 comprises the sum of thicknesses of the first substrate 110, thesecond substrate 130, and the interlayer 120. In various embodiments,the laminate 100 may have a thickness in the range of about 1.8 mm toabout 6.85 mm, or in the range of about 1.8 mm to about 5.85 mm, or inthe range of about 1.8 mm to about 5.0 mm, or 2.1 mm to about 6.85 mm,or in the range of about 2.1 mm to about 5.85 mm, or in the range ofabout 2.1 mm to about 5.0 mm, or in the range of about 2.4 mm to about6.85 mm, or in the range of about 2.4 mm to about 5.85 mm, or in therange of about 2.4 mm to about 5.0 mm, or in the range of about 3.4 mmto about 6.85 mm, or in the range of about 3.4 mm to about 5.85 mm, orin the range of about 3.4 mm to about 5.0 mm.

In one or more embodiments, the laminate 100 exhibits radii of curvaturethat is less than 1000 mm, or less than 750 mm, or less than 500 mm, orless than 300 mm. The laminate, the first substrate and/or the secondsubstrate are substantially free of wrinkles.

In one or more embodiments the second substrate 130 is relatively thinin comparison to the first substrate. In other words, the firstsubstrate 110 has a thickness greater than the second substrate 130. Inone or more embodiments, the first substrate 110 may have a thicknessthat is more than two times the thickness of the second substrate 130.In one or more embodiments, the first substrate 110 may have a thicknessin the range from about 1.5 times to about 2.5 times the thickness ofthe second substrate 130.

In one or more embodiments, the first substrate 110 and the secondsubstrate 130 may have the same thickness, wherein the first substrateis more rigid or has a greater stiffness than the second substrate, andin very specific embodiments, both the first substrate and the secondsubstrate have a thickness in the range of 0.2 mm and 0.7 mm.

In one or more specific embodiments, the second substrate 130 has athickness of 0.8 mm or less. In various embodiments, the secondsubstrate 130 may have a thickness in the range of about 0.1 mm to about1.4 mm, or in the range of about 0.2 mm to about 1.4 mm, or in the rangeof about 0.3 mm to about 1.4 mm, or in the range of about 0.4 mm toabout 1.4 mm, or in the range of about 0.5 mm to about 1.4 mm, or in therange of about 0.1 mm to about 1 mm, or in the range of about 0.2 mm toabout 1 mm, or in the range of about 0.1 mm to about 0.7 mm, or in therange of about 0.2 mm to about 0.7 mm, or in the range of about 0.3 mmto about 0.7 mm, or in the range of about 0.4 mm to about 0.7 mm, or inthe range of about 0.2 mm to about 0.6 mm, or in the range of about 0.3mm to about 0.6 mm, or in the range of about 0.4 mm to about 0.6 mm, orin the range of about 0.2 mm to about 0.5 mm, or in the range of about0.3 mm to about 0.5 mm, or in the range of about 0.2 mm to about 0.4 mm.

In one or more embodiments, the first substrate 110 may have a thicknessgreater than the second substrate 130. In one or more embodiments, thefirst substrate 110 has a thickness of 4.0 mm or less, or 3.85 mm orless. In various embodiments, the first substrate may have a thicknessin the range of about 1.4 mm to about 3.85 mm, or in the range of about1.4 mm to about 3.5 mm, or in the range of about 1.4 mm to about 3.0 mm,or in the range of about 1.4 mm to about 2.8 mm, or in the range ofabout 1.4 mm to about 2.5 mm, or in the range of about 1.4 mm to about2.0 mm, or in the range of about 1.5 mm to about 3.85 mm, or in therange of about 1.5 mm to about 3.5 mm, or in the range of about 1.5 mmto about 3.0 mm, or in the range of about 1.5 mm to about 2.8 mm, or inthe range of about 1.5 mm to about 2.5 mm, or in the range of about 1.5mm to about 2.0 mm, or in the range of about 1.6 mm to about 3.85 mm, orin the range of about 1.6 mm to about 3.5 mm, or in the range of about1.6 mm to about 3.0 mm, or in the range of about 1.6 mm to about 2.8 mm,or in the range of about 1.6 mm to about 2.5 mm, or in the range ofabout 1.6 mm to about 2.0 mm, or in the range of about 1.8 mm to about3.5 mm, or in the range of about 2.0 mm to about 3.0 mm.

The materials for the first substrate 110 and the second substrate 130may be varied. According to one or more embodiments, the materials forthe first substrate and the second substrate may be the same material ordifferent materials. In exemplary embodiments, one or both of the firstsubstrate and second substrate may be glass (e.g., soda lime glass,alkali aluminosilicate glass, alkali containing borosilicate glassand/or alkali aluminoborosilicate glass) or glass-ceramic. Examples ofsuitable glass ceramics include Li₂O—Al₂O₃—SiO₂ system (i.e. LAS-System)glass ceramics, MgO—Al₂O₃—SiO₂ system (i.e. MAS-System) glass ceramics,and glass ceramics including crystalline phases of any one or more ofmullite, spinel, α-quartz, β-quartz solid solution, petalite, lithiumdissilicate, β-spodumene, nepheline, and alumina. Furthermore, one orboth of the first substrate and second substrate can be strengthenedchemically, thermally, mechanically or a combination thereof. In one ormore embodiments, the first substrate is unstrengthened (which means notstrengthened by chemical strengthening, thermal strengthening ormechanical strengthening processes, but may include an annealedsubstrate) and the second substrate is strengthened. In one or morespecific embodiments, the second glass substrate is chemicallystrengthened.

In one or more embodiments, a laminate may include one or both of thesubstrates being made of glass or a material other than glass, forexample plastic, metal, ceramic, glass-ceramic, wood, and combinationsthereof.

The substrates may be provided using a variety of different processes.For instance, where a substrate includes a glass substrate, exemplaryglass substrate forming methods include float glass processes anddown-draw processes such as fusion draw and slot draw.

A glass substrate prepared by a float glass process may be characterizedby smooth surfaces and uniform thickness is made by floating moltenglass on a bed of molten metal, typically tin. In an example process,molten glass that is fed onto the surface of the molten tin bed forms afloating glass ribbon. As the glass ribbon flows along the tin bath, thetemperature is gradually decreased until the glass ribbon solidifiesinto a solid glass substrate that can be lifted from the tin ontorollers. Once off the bath, the glass substrate can be cooled furtherand annealed to reduce internal stress.

Down-draw processes produce glass substrates having a uniform thicknessthat possess relatively pristine surfaces. Because the average flexuralstrength of the glass substrate is controlled by the amount and size ofsurface flaws, a pristine surface that has had minimal contact has ahigher initial strength. Down-drawn glass substrates may be drawn to athickness of less than about 2 mm.

The fusion draw process, for example, uses a drawing tank that has achannel for accepting molten glass raw material. The channel has weirsthat are open at the top along the length of the channel on both sidesof the channel. When the channel fills with molten material, the moltenglass overflows the weirs. Due to gravity, the molten glass flows downthe outside surfaces of the drawing tank as two flowing glass films.These outside surfaces of the drawing tank extend down and inwardly sothat they join at an edge below the drawing tank. The two flowing glassfilms join at this edge to fuse and form a single flowing glasssubstrate. The fusion draw method offers the advantage that, because thetwo glass films flowing over the channel fuse together, neither of theoutside surfaces of the resulting glass substrate comes in contact withany part of the apparatus. Thus, the surface properties of the fusiondrawn glass substrate are not affected by such contact.

The slot draw process is distinct from the fusion draw method. In slowdraw processes, the molten raw material glass is provided to a drawingtank. The bottom of the drawing tank has an open slot with a nozzle thatextends the length of the slot. The molten glass flows through theslot/nozzle and is drawn downward as a continuous substrate and into anannealing region.

Once formed, either one of the first substrate or the second substratemay be strengthened to form a strengthened glass substrate. It should benoted that glass ceramic substrates may also be strengthened in the samemanner as glass substrates. As used herein, the term “strengthenedsubstrate” may refer to a glass substrate or a glass ceramic substratesthat has been strengthened, for example through chemical strengthening(e.g., ion-exchange of larger ions for smaller ions in the surface ofthe glass or glass ceramic substrate), by thermal strengthening, ormechanical strengthening. In some embodiments, the substrates may bestrengthened using a combination of any one or more of chemicalstrengthening processes, thermal strengthening processes and mechanicalstrengthening processes.

In one or more embodiments, the strengthened substrates described hereinmay be chemically strengthened by an ion exchange process. In theion-exchange process, typically by immersion of a glass or glass ceramicsubstrate into a molten salt bath for a predetermined period of time,ions at or near the surface(s) of the glass or glass ceramic substrateare exchanged for larger metal ions from the salt bath. In oneembodiment, the temperature of the molten salt bath is in the range fromabout 350° C. to about 430° C. and the predetermined time period isabout two hours to about eight hours. The incorporation of the largerions into the glass or glass ceramic substrate strengthens the substrateby creating a compressive stress (CS) in a near surface region or inregions at and adjacent to the surface(s) of the substrate. Acorresponding tensile stress is induced within a central region orregions at a distance from the surface(s) of the substrate to balancethe compressive stress. The central region or regions exhibiting atensile stress are referred to as a central tension (CT) region). Glassor glass ceramic substrates utilizing this strengthening process may bedescribed more specifically as chemically-strengthened or ion-exchangedglass or glass ceramic substrates.

In one example, sodium ions in a glass or glass ceramic substrate arereplaced by potassium ions from the molten bath, such as a potassiumnitrate salt bath, though other alkali metal ions having larger atomicradii, such as rubidium or cesium, can replace smaller alkali metal ionsin the glass. According to particular embodiments, smaller alkali metalions in the glass or glass ceramic can be replaced by Ag+ ions.Similarly, other alkali metal salts such as, but not limited to,sulfates, phosphates, halides, and the like may be used in the ionexchange process.

The compressive stress is related to the central tension by thefollowing expression (1):

${CS} = {C{T\left( \frac{t - {2DOL}}{DOL} \right)}}$where t is the total thickness of the strengthened glass or glassceramic substrate and compressive depth of layer (DOL) is the depth ofexchange. DOL refers to the depth in the glass or glass ceramicsubstrate at which compressive stress switches to tensile stress.

Where thermal strengthening is used, the glass or glass ceramicsubstrates may be heated and then cooled using very high heat transferrates (h in units of cal/cm²-s-C°) in a precise manner, with goodphysical control and gentle handling of the glass. In particularembodiments, the thermal strengthening processes and systems may utilizea small-gap, gas bearing in the cooling/quenching section that allowsprocessing thin glass substrates at higher relative temperatures at thestart of cooling, resulting in higher thermal strengthening levels. Asdescribed below, this small-gap, gas bearing cooling/quenching sectionachieves very high heat transfer rates via conductive heat transfer toheat sink(s) across the gap, rather than using high air flow basedconvective cooling. This high rate conductive heat transfer is achievedwhile not contacting the glass with liquid or solid material, bysupporting the glass substrate on gas bearings within the gap.

In one or more embodiments, the resulting thermally strengthened glassor glass ceramic substrate exhibits higher levels of permanent thermallyinduced stresses than previously known. Without wishing to be bound bytheory, it is believed that the achieved levels of thermally inducedstress are obtainable for a combination of reasons. The high uniformityof the heat transfer in the processes detailed herein reduces or removesphysical and unwanted thermal stresses in the glass, allowing glasssubstrates to be tempered at higher heat transfer rates withoutbreaking. Further, the present methods can be performed at lower glasssubstrate viscosities (higher initial temperatures at the start ofquench), while still preserving the desired glass flatness and form,which provides a much greater change in temperature in the coolingprocess, thus increasing the heat strengthening levels achieved.

In various embodiments, the thermally strengthened glass or glassceramic substrate have both the stress profiles described herein and alow, as-formed surface roughness. The processes and methods disclosedherein can thermally strengthen the substrates without increasing thesurface roughness of the as-formed surfaces. For example, incoming floatglass air-side surfaces and incoming fusion formed glass surfaces werecharacterized by atomic force microscopy (AFM) before and afterprocessing. R_(a) surface roughness was less than 1 nm (0.6-0.7 nm) forincoming 1.1 mm soda-lime float glass, and the R_(a) surface roughnesswas not increased by thermal strengthening according to the presentprocesses. Similarly, an R_(a) surface roughness of less than 0.3 nm(0.2-0.3) for 1.1 mm sheets of fusion-formed glass was maintained bythermal strengthening according to this disclosure. Accordingly,thermally strengthened glass and glass ceramic substrates according oneor more embodiments have a surface roughness on at least a first surfacein the range from 0.2 to 1.5 nm R_(a) roughness, 0.2 to 0.7 nm, 0.2 to0.4 nm or even such as 0.2 to 0.3 nm, over at least an area of 10×10 μm.Surface roughness may be measured over an area of 10×10 μmin exemplaryembodiments, or in some embodiments, 15×15 μm.

In another embodiment, the thermally strengthened glass or glass ceramicsubstrates described herein have high flatness. In various embodiments,the strengthening system discussed herein utilizes controlled gasbearings to support the glass or glass ceramic substrate duringtransporting and heating, and in some embodiments, can be used to assistin controlling and/or improving the flatness of the resulting thermallystrengthened glass or glass ceramic substrate, resulting in a higherdegree of flatness than previously obtainable, particularly for thinand/or highly strengthened glass or glass ceramic substrates. Forexample, glass or glass ceramic substrates in sheet form having athickness of about 0.6 mm or greater can be strengthened with improvedpost-strengthening flatness. The flatness of various embodiments of thethermally strengthened glass or glass ceramic substrate can comprise 100μm or less total indicator run-out (TIR) along any 50 mm length alongone of the first or second surfaces thereof, 300 μm TIR or less within a50 mm length on one of the first or second surfaces, 200 μm TIR or less,100 μm TIR or less, or 70 μm TIR or less within a 50 mm length on one ofthe first or second surfaces. In exemplary embodiments, flatness ismeasured along any 50 mm or less profile of the thermally strengthenedglass or glass ceramic substrates. In contemplated embodiments, thethermally strengthened glass or glass ceramic substrates, which may bein sheet form, with thickness disclosed herein have flatness of 200 μmTIR or less within a 20 mm length on one of the first or second surfaces(e.g., flatness of 100 μm TIR or less, flatness 70 μm TIR or less, orflatness 50 μm TIR or less).

According to contemplated embodiments, the thermally strengthened glassor glass ceramic substrates according to one or more embodiments have ahigh-degree of dimensional consistency such that the thickness t thereofalong a 1 cm length or width does not change by more than 50 μm, suchas, by not more than 10 μm, not more than 5 μm, not more than 2 μm. Suchdimensional consistency may not be achievable for given thicknesses,areas, and/or magnitudes of negative tensile stress, as disclosedherein, by solid quenching due to practical considerations, such ascooling plate alignment and/or surface irregularities that may distortthe dimensions.

According to contemplated embodiments, the thermally strengthened glassor glass ceramic substrates according to one or more embodiments have atleast one surface that is flat such that a 1 cm lengthwise profiletherealong stays within 50 μm of a straight line, such as within 20 μm,10 μm, 5 μm, 2 μm; and/or a 1 cm widthwise profile therealong stayswithin 50 μm of a straight line, such as within 20 μm, 10 μm, 5 μm, 2μm. Such high flatness may not be achievable for given thicknesses,areas, and/or magnitudes of negative tensile stress, as disclosedherein, by liquid quenching due to practical considerations, such aswarping or bending of the glass strengthened in these processes due toconvective currents and associated forces of the liquid.

In various embodiments, the thermally strengthened glass or glassceramic substrates according to one or more embodiments have highfictive temperatures. It will be understood that in various embodiments,high fictive temperatures relate to the high level of thermalstrengthening, high central tensile stresses and/or high compressivesurface stress of the resulting glass or glass ceramic substrate.Surface fictive temperatures may be determined by any suitable method,including differential scanning calorimetry, Brillouin spectroscopy, orRaman spectroscopy.

According to an exemplary embodiment, the thermally strengthened glassor glass ceramic substrates according to one or more embodiments has aportion thereof, such as at or near the surfaces, that has aparticularly high fictive temperature, such as at least 500° C., such asat least 600° C., or even at least 700° C. In some embodiments, theglass or glass ceramic substrate that exhibits such fictive temperaturesmay include a soda-lime glass. According to an exemplary embodiment, thethermally strengthened glass or glass ceramic substrates according toone or more embodiments has a portion thereof, such as at or near thesurfaces, that has a particularly high fictive temperature relative toannealed glass of the same chemical composition. For example, in someembodiments, the thermally strengthened glass or glass ceramicsubstrates exhibit a fictive temperature that is least 10° C. greater,at least 30° C. greater, at least 50° C. greater, at least 70° C.greater, or even at least 100° C. greater than the fictive temperatureof an annealed glass of the same chemical composition (i.e., a glassthat is and has not been thermally strengthened according to the processdescribed herein). High fictive temperature may be achieved by a rapidtransition from the hot to the cooling zones in the thermalstrengthening system. Without being bound by theory, thermallystrengthened glass or glass ceramic substrates with high fictivetemperature exhibit increased damage resistance.

In some methods of determining surface fictive temperatures, it may benecessary to break the thermally strengthened glass or glass ceramicsubstrate to relieve the “temper stresses” induced by the heatstrengthening process in order to measure fictive temperature withreasonably accuracy. It is well known that characteristic structurebands measured by Raman spectroscopy shift in a controlled manner bothwith respect to the fictive temperature and with respect to appliedstress in silicate glasses. This shift can be used to non-destructivelymeasure the fictive temperature if the temper stress is known. Themethod of determining fictive temperature is described in U.S.Provisional Patent Application No. 62/236,296, entitled “THERMALLYSTRENGTHENED GLASS AND RELATED SYSTEMS AND METHODS”, filed on Oct. 2,2015, the content of which is incorporated herein, in its entirety, byreference.

The following non-dimensional fictive temperature parameter θ can beused to compare the relative performance of a thermal strengtheningprocess in terms of the fictive temperature produced. Given in terms ofsurface fictive temperature θs in this case:θs=(T _(fs) −T _(anneal))/(T _(soft) −T _(anneal))  (2)where T_(fs) is the surface fictive temperature, T_(anneal) (thetemperature of the glass at a viscosity of η=10^(13.2) Poise) is theannealing point and T_(soft) (the temperature of the glass at aviscosity of η=10^(7.6) Poise) is the softening point of the glass ofthe sheet. FIG. 10 is a plot of θs for measured surface fictivetemperatures as a function of heat transfer rate, h, applied duringthermal strengthening for two different glasses. In one or moreembodiments, a thermally strengthened glass or glass ceramic comprises aglass having a softening temperature, expressed in units of ° C., ofT_(soft) and an annealing temperature, expressed in units of ° C., ofT_(anneal), and a surface fictive temperature measured on the firstsurface of the glass sheet represented by Tfs, when expressed in unitsof ° C. and a non-dimensional surface fictive temperature parameter θsgiven by (Tfs−T_(anneal))/(T_(soft)−T_(anneal)), wherein the parameterθs is in the range of from 0.20 to 0.9. In embodiments, parameter θscomprises from about (e.g., plus or minus 10%) 0.21 to 0.09, or 0.22 to0.09, or 0.23 to 0.09, or 0.24 to 0.09, or 0.25 to 0.09, or 0.30 to0.09, or 0.40 to 0.09, or 0.5 to 0.9, or 0.51 to 0.9, or 0.52 to 0.9, or0.53 to 0.9, or 0.54 to 0.9, or 0.54 to 0.9, or 0.55 to 0.9, or 0.6 to0.9, or even 0.65 to 0.9.

At higher thermal transfer rates (such as at about 800 W/m²K and above,for example), however, the high temperature or “liquidus” CTE of theglass begins to affect tempering performance. Therefore, under suchconditions, the temperability parameter Ψ, based on an approximation ofintegration over the changing CTE values across the viscosity curve, isfound to be useful:Ψ=E·[T _(strain)·α_(CTE) ^(S)+α_(CTE) ^(L)·(T _(soft) −T_(strain))]  (3)where α^(S) _(CTE) is the low temperature linear CTE (equivalent to theaverage linear expansion coefficient from 0-300° C. for the glass),expressed in 1/° C. (° C.⁻¹), α^(L) _(CTE) is the high temperaturelinear CTE (equivalent to the high-temperature plateau value which isobserved to occur somewhere between the glass transition and softeningpoint), expressed in 1/° C. (° C.⁻¹), E is the elastic modulus of theglass, expressed in GPa (not MPa) (which allows values of the(non-dimensional) parameter Ψ to range generally between 0 and 1),T_(strain) is the strain point temperature of the glass, (thetemperature of the glass at a viscosity of η=10^(14.7) Poise) expressedin ° C., and T_(soft) is the softening point of the glass (thetemperature of the glass at a viscosity of η=10^(7.6) Poise), expressedin ° C.

The thermal strengthening process and resulting surface CS values weremodeled for glasses having varying properties to determine the temperingparameter, Ψ. The glasses were modeled at the same starting viscosity of10^(8.2) Poise and at varying heat transfer coefficients. The propertiesof the various glasses are shown in Table 1, together with thetemperature for each glass at 10^(8.2) Poise and the calculated value ofthe temperability parameter Ψ for each.

TABLE 1 10^(8.2) Softening Strain CTE CTE Poise Point Point GlassModulus low high ° C. (° C.) (° C.) Ψ SLG 72 8.8 27.61 705 728 507 0.762 73.3 8.53 20.49 813 837 553 0.77 3 65.5 8.26 26 821 862 549 0.83 4 658.69 20.2 864 912 608 0.74 5 63.9 10.61 22 849 884 557 0.84 6 58.26 3.520.2 842 876 557 0.49 7 73.6 3.6 13.3 929 963 708 0.44 8 81.1 3.86 12.13968 995 749 0.48

The results in Table 2 show that Ψ is proportional to the thermalstrengthening performance of the glass. In another aspect, it has beenfound that for any glass, at any given value of the heat transfercoefficient, h (expressed in cal/cm²-s-° C.), the curves of surface CS(σ_(CS), in MPa) vs. thickness (t, in mm) can be fit (over the range oft from 0 to 6 mm) by the hyperbola, where P₁ and P₂ are functions of hsuch that:

$\begin{matrix}{{\sigma_{CS}\left( {{Glass},h,t} \right)} = {{{C\left( {h,t} \right)}*{\Psi({Glass})}} = {\frac{{P_{1}(h)}*t}{\left( {{P_{2}(h)} + t} \right)}*{\Psi({Glass})}}}} & (4)\end{matrix}$or with the expression for substituted in, the curve of CSσ_(OS)(Glass,h,t) is given by:

$\begin{matrix}{\frac{{P_{1}(h)}*t}{\left( {{P_{2}(h)} + t} \right)} \cdot E \cdot \left\lbrack {{T_{strain} \cdot \alpha_{CTE}^{s}} + {\alpha_{CTE}^{L} \cdot \left( {T_{soft} - T_{strain}} \right)}} \right\rbrack} & (5)\end{matrix}$where the constants P₁, P₂, in either (4) or (5) above, are eachcontinuous functions of the heat transfer value, h, given by:

$\begin{matrix}{P_{1} = {910.2 - {259.2 \cdot {\exp\left( {- \frac{h}{0.145}} \right)}}}} & (6) \\{and} & \; \\{P_{2} = {2.53 + \frac{23.65}{\left( {1 + \left( \frac{h}{0.00758} \right)^{1.85}} \right)}}} & (7)\end{matrix}$

In some embodiments, a similar expression may be used to predict the CTof a thermally strengthened glass sheet, particularly at a thickness of6 mm and less, and the thermal transfer coefficient, such as 800 W/m²Kand up, by simply dividing the CS predicted under the same conductionsby 2. Thus, expected CT may be given by

$\begin{matrix}{\frac{{P_{1{CT}}\left( h_{CT} \right)}*t}{\left( {{P_{2{CT}}\left( h_{CT} \right)} + t} \right)} \cdot E \cdot \left\lbrack {{T_{strain} \cdot \alpha_{CTE}^{s}} + {\alpha_{CTE}^{L} \cdot \left( {T_{soft} - T_{strain}} \right)}} \right\rbrack} & (8)\end{matrix}$Where P_(1CT) and P_(2CT) are given as follows:

$\begin{matrix}{P_{1{CT}} = {910.2 - {259.2 \cdot {\exp\left( {- \frac{h_{CT}}{0.145}} \right)}}}} & (9) \\{and} & \; \\{P_{2{CT}} = {2.53 + \frac{23.65}{\left( {1 + \left( \frac{h_{CT}}{0.00758} \right)^{1.49}} \right)}}} & (10)\end{matrix}$In some embodiments, h and h_(CT), may have the same value for a givenphysical instance of thermal strengthening. However, in someembodiments, they may vary, and providing separate variables andallowing variation between them allows for capturing, within descriptiveperformance curves, instances in which the typical ratio of 2:1 CS/CTdoes not hold.

One or more embodiments of the currently disclosed processes and systemshave produced thermally strengthened SLG sheets at all of the heattransfer rate values (h and h_(CT)) shown in Table 2.

TABLE 2 h and h_(CT) values according to exemplary embodiments cal/s ·cal/s · cal/s · cm² · ° C. W/m2K cm2 · ° C. W/m2K cm2 · ° C. W/m2K 0.010418.68 0.042 1758.456 0.070 2930.76 0.013 544.284 0.045 1884.06 0.0712972.628 0.018 753.624 0.047 1967.796 0.078 3265.704 0.019 795.492 0.0482009.664 0.080 3349.44 0.020 837.36 0.049 2051.532 0.081 3391.308 0.021879.228 0.050 2093.4 0.082 3433.176 0.022 921.096 0.051 2135.268 0.0953977.46 0.023 962.964 0.052 2177.136 0.096 4019.328 0.027 1130.436 0.0532219.004 0.102 4270.536 0.028 1172.304 0.054 2260.872 0.104 4354.2720.029 1214.172 0.055 2302.74 0.105 4396.14 0.030 1256.04 0.060 2512.080.127 5317.236 0.031 1297.908 0.061 2553.948 0.144 6028.992 0.0331381.644 0.062 2595.816 0.148 6196.464 0.034 1423.512 0.063 2637.6840.149 6238.332 0.038 1590.984 0.065 2721.42 0.184 7703.712 0.040 1674.720.067 2805.156 0.041 1716.588 0.069 2888.892

In some embodiments, the heat transfer value rates (h and h_(CT)) may befrom about 0.024 to about 0.15, about 0.026 to about 0.10, or about0.026 to about 0.075 cal/s·cm²·° C.

In one or more embodiments, the strengthened glass or glass ceramicsubstrate may be mechanically strengthened by utilizing a mismatch ofthe coefficient of thermal expansion between portions of the substrateto create compressive stress and central tension regions.

In one embodiment, a strengthened glass or glass ceramic substrate canhave a surface CS of 300 MPa or greater, e.g., 400 MPa or greater, 450MPa or greater, 500 MPa or greater, 550 MPa or greater, 600 MPa orgreater, 650 MPa or greater, 700 MPa or greater, 750 MPa or greater or800 MPa or greater. In one or more embodiments, the surface CS is themaximum CS in the strengthened glass or glass ceramic substrate.

The strengthened glass or glass ceramic substrate may have a DOL ofabout 15 μm or greater, 20 μm or greater (e.g., 25 μm, 30 μm, 35 μm, 40μm, 45 μm, 50 μm or greater). In one or more embodiments, thestrengthened glass or glass ceramic substrate may exhibit a maximum CTvalue of 10 MPa or greater, 20 MPa or greater, 30 MPa or greater, 40 MPaor greater (e.g., 42 MPa, 45 MPa, or 50 MPa or greater) but less than100 MPa (e.g., 95, 90, 85, 80, 75, 70, 65, 60, 55 MPa or less).

In one or more specific embodiments, the strengthened glass or glassceramic substrate has one or more of the following: a surfacecompressive stress greater than 300 MPa, a depth of compressive layergreater than 15 μm, and a central tension greater than 18 MPa.

Examples of glasses that may be used in the substrate may include alkalialuminosilicate glass compositions or alkali aluminoborosilicate glasscompositions, though other glass compositions are contemplated. Oneexample glass composition comprises SiO₂, B₂O₃ and Na₂O, where(SiO₂+B₂O₃)≥66 mol. %, and Na₂O≥9 mol. %. In an embodiment, the glasscomposition includes at least 6 wt. % aluminum oxide. In a furtherembodiment, the substrate includes a glass composition with one or morealkaline earth oxides, such that a content of alkaline earth oxides isat least 5 wt. %. Suitable glass compositions, in some embodiments,further comprise at least one of K₂O, MgO, and CaO. In a particularembodiment, the glass compositions used in the substrate can comprise61-75 mol. % SiO2; 7-15 mol. % Al₂O₃; 0-12 mol. % B₂O₃; 9-21 mol. %Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and 0-3 mol. % CaO.

A further example glass composition suitable for the substratecomprises: 60-70 mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15mol. % Li₂O; 0-20 mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10mol. % CaO; 0-5 mol. % ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂; less than50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 12 mol.%≤(Li₂O+Na₂O+K₂O)≤20 mol. % and 0 mol. % (MgO+CaO)≤10 mol. %.

A still further example glass composition suitable for the substratecomprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.%≤(Li₂O+Na₂O+K₂O)≤18 mol. % and 2 mol. %≤(MgO+CaO) 7 mol. %.

In a particular embodiment, an alkali aluminosilicate glass compositionsuitable for the substrate comprises alumina, at least one alkali metaland, in some embodiments, greater than 50 mol. % SiO₂, in otherembodiments at least 58 mol. % SiO₂, and in still other embodiments atleast 60 mol. % SiO₂, wherein the ratio ((Al₂O₃+B₂O₃)/Σmodifiers)>1,where in the ratio the components are expressed in mol. % and themodifiers are alkali metal oxides. This glass composition, in particularembodiments, comprises: 58-72 mol. % SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol.% B₂O₃; 8-16 mol. % Na₂O; and 0-4 mol. % K₂O, wherein the ratio((Al₂O₃+B₂O₃)/Σmodifiers)>1.

In still another embodiment, the substrate may include an alkalialuminosilicate glass composition comprising: 64-68 mol. % SiO₂; 12-16mol. % Na₂O; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂Od; 2-5 mol. % K₂O; 4-6mol. % MgO; and 0-5 mol. % CaO, wherein: 66 mol. %≤SiO₂+B₂O₃+CaO≤69 mol.%; Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na₂O+B₂O₃)—Al₂O₃≤2 mol. %; 2 mol. %≤Na₂O—Al₂O₃≤6 mol. %; and 4 mol.%≤(Na₂O+K₂O)—Al₂O₃≤10 mol. %.

In an alternative embodiment, the substrate may comprise an alkalialuminosilicate glass composition comprising: 2 mol % or more of Al₂O₃and/or ZrO₂, or 4 mol % or more of Al₂O₃ and/or ZrO₂.

In some embodiments, the compositions used for a glass substrate may bebatched with 0-2 mol. % of at least one fining agent selected from agroup that includes Na₂SO₄, NaCl, NaF, NaBr, K₂SO₄, KCl, KF, KBr, andSnO₂.

In one or more embodiments, the interlayer 120 comprises a materialselected from the group consisting of polyvinyl butyral (PVB) resin,ethylenevinylacetate copolymer (EVA), ionomers, polyvinyl chloridecopolymers and thermoplastic polyurethanes (TPUs). The thickness of theinterlayer may be in the range from about 0.3 mm to about 2 mm.

In one or more embodiments, the laminate may have a length and width inthe range of 30.5 cm by about 30.5 cm (12 in.×12 in.) to about 50.8 cmby 101.6 cm (20 in.×40 in.), or to about 121.9 cm by 127 cm (48 in.×50in.), or to about 127 cm by 183 cm (50 in.×72 in.). While the laminateshave been described in terms of two dimensions, it should be understoodthat laminates may have various shapes, including quadrilaterals (e.g.,rectangular, square, trapezoid, etc.), triangles having dimensions intwo directions, for example along two different sides or axis of aplane, or may have non-rectangular shapes (e.g., circular, elliptical,oval, polygonal, etc.) that may be described in terms of a radius and/orthe length of major and minor axis, where the non-rectangular shapes maybe related to a rectangular shape corresponding to the two largestdimensions in perpendicular directions, for example, as it would bemeasured to be cut out of a rectangular substrate. The substrates may besuitably configured and dimensioned to laminates of an intended size.

In one or more embodiments, the laminate may have additional coating orlayers applied to the exposed surfaces, including but not limited totints, anti-reflection coatings, anti-glare coatings, scratch resistantcoatings, etc. In one or more embodiments, the polymer interlayer can bemodified to have one or more of the following properties: ultraviolet(UV) absorption, Infrared (IR) absorption, IR reflection and tint. Thepolymer interlayer can be modified by a suitable additive such as a dye,a pigment, dopants, etc. to impart the desired property.

A second aspect of this disclosure pertains to methods of cold-formingthe laminates described herein. FIG. 2 illustrates a cross-sectionalview of an exemplary embodiment of the first substrate 110, theinterlayer 120, and the second substrate 130 before cold-forming.

First substrate 110 is arranged in a stack with interlayer 120 and thesecond substrate 130. As shown in FIG. 2, the second substrate 130 isflat prior to the forming process. In various embodiments, during acold-forming process, pressure is applied to the stack such that thesecond substrate 130, the interlayer 120, and the first substrate 110are pressed together by applying pressure to the stack as shown by thearrows “P” in FIG. 2. In one or more embodiments, the pressure may beabout 1 atmosphere or greater. In one or more alternative embodiments,the pressure applied may be about 1 atmosphere or less. As describedfurther below, heat may be applied at a temperature below the formingtemperature of the second substrate 130. The second substrate 130deforms to take on the shape of the first substrate 110 and the firstsubstrate 110 and the second substrate are bonded together by theinterlayer 120. The second substrate 130, first substrate 110 having thecomplexly curved shape, and interlayer 120 are thus laminated togetherby the cold-forming process to form the laminate 100, as shown inFIG. 1. In one or more embodiments, the first glass substrate 110 couldalso be annealed or thermally tempered.

In one or more embodiments, the first and second substrates may bestacked, aligned, and introduced into the cold-forming apparatus at thesame time. The multiple substrates may then be shaped and cold-formedtogether at one time by the bending apparatus.

In one or more embodiments, the method includes hot forming the firstsubstrate to a complexly curved shape prior to cold-forming the firstsubstrate and the second substrate into one or more embodiments of thelaminates described herein. In one or more embodiments, hot forming thefirst substrate may include heating the first substrate to a temperaturenear the softening point of the substrate and then bending the heatedfirst substrate to the complexly curved shape. In one or moreembodiments, the first substrate is a glass substrate and hot formingthe first substrate includes heating the first substrate to atemperature near the softening point, e.g., above 400° C.

In one or more embodiments, the complexly curved first substrate and theflat second substrate are cold-formed into a laminate at a temperaturewell below the softening point of the second substrate. In one or moreembodiments, the cold-forming process occurs at a temperature that is200° C. or more below the softening point of the substrate. Softeningpoint refers to the temperature at which glass will deform under its ownweight. In one or more specific embodiments, the temperature during thecold-forming process is below about 400° C., below about 350° C., belowabout 300° C., below about 200° C., below about 175° C. or below about150° C. In one specific embodiment the cold-forming process is in therange of room temperature to about 140° C. Room temperature can beconsidered to be the ambient temperature of a production floor (e.g.,16° C. to about 35° C.).

In one or more embodiments, the method includes disposing an interlayerbetween a complexly curved first substrate and a flat second substrate,and cold-forming the substrates so that the flat substrate becomescomplexly curved, while simultaneously bonding the two substratestogether via the interlayer. In one or more embodiments, the methodincludes bonding the first and second substrates together via theinterlayer in a separate step from the cold-forming step in which theflat second substrate is shaped to conform to the first substrate. Invarious embodiments, the bonding step includes heating the stack of thefirst substrate, the interlayer and the second substrate to atemperature in the range of about 100° C. to about 140° C. to form abond between the substrates and the interlayer. In one or moreembodiments, the method may include the use of an adhesive in additionto or instead of the interlayer to bond the substrates together.

In one or more embodiments, the method does not include bonding thefirst and second substrates. In such embodiments, the complexly curvedfirst substrate and the flat second substrate are stacked and alignedtogether, and pressed together to shape the second substrate into acomplexly curved shape that conforms to the shape of the firstsubstrate. The two substrates are then separated and used individually.

In one or more embodiments, during the cold-forming process, the secondsubstrate deforms to fit against a second surface 114 of the firstsubstrate and a peripheral portion of the second substrate exerts acompressive force against the interlayer (when present) and firstsubstrate due to the desire to flex back to a flatter state. A centerportion of the second substrate exerts a tensile force against theinterlayer (when present) and the first substrate as it attempts to pullaway from the interlayer to flex back to a flatter state to relieve atleast a portion of tensile stress.

The embodiments of the method described herein enable highermanufacturing yields because the second substrate can have a large rangeof shapes and still be successfully cold-formed to the first substrate.According to one or more embodiments, where the second substrate isglass, the methods described herein overcome shape mismatch that canoccur during glass forming and result in a laminate having a desirableand repeatable shape, even when the second substrate lacks shapeuniformity.

In one or more embodiments, the cold-forming process may be performed ona press-bending apparatus comprising a male mold form and a female moldform. In various embodiments, the second substrate may be supported bythe female mold form, and provides a hollow space in at least a middleportion to receive a portion of the second substrate during a formingoperation. In various embodiments, the female bending form and the malebending form are configured to engage each other to cold-form the secondsubstrate and first substrate into the laminate.

In various embodiments, a vacuum technique may be used to cold-form thefirst and second substrates into the laminates described herein.Suitable vacuum techniques include a vacuum bag technique or vacuumrings and can also be used. In alternative embodiments, flat bed clamshell type laminating machine can be used.

In a vacuum bag technique, the first substrate, the second substrateand, optionally, the interlayer, may be stacked and aligned and placedin a suitable bag. The air is extracted from the bag until theatmospheric pressure surrounding the bag applies a force ofapproximately one atmosphere (i.e., taking into accountelevation/geographical location, and limits of the vacuum apparatus toevacuate all the air, etc.). In various embodiments, the force appliedcauses the second substrate to cold-form to the complexly curved firstsubstrate.

A third aspect of this disclosure relates to a vehicle including a bodyhaving an opening and one or more embodiments of the laminates disclosedherein disposed in the opening. The vehicle may include an automobile, aheavy duty truck, sea craft, rail cars, air craft, and the like. Thelaminate may be movable with respect to the opening.

A fourth aspect of this disclosure pertains to a vehicle having a bodydefining an interior cabin, wherein the interior cabin comprises asurface formed from one or more laminates described herein. In one ormore embodiments, the surface forms at least a portion of the dashboard,floorboard, door panel, center console, instrument panels, displaypanel, head rest, pillar and the like.

EXAMPLES

Principles and embodiments of the disclosure are exemplified by thefollowing non-limiting examples.

Examples using methods described herein were prepared by laminating aflat, chemically strengthened substrate (formed from an alkalialuminosilicate glass) to a complexly curved unstrengthened substrate(formed from soda lime glass (SLG)) having a thickness greater than theflat, chemically strengthened substrate. The resulting laminatesincluded a trilayer acoustic polyvinyl butyrate interlayer between thesubstrates. The laminate was also formed using a vacuum technique witheither vacuum bags or vacuum channel de-airing and a standard autoclaveprocesses.

Example 1

A glass substrate having a diameter of 355.6 mm and thickness of 0.7 mmformed from an aluminosilicate glass composition (labeled “GG”) wasassembled in a stack with a glass substrate having the same diameter anda thickness of 1.6 mm formed from a SLG (labeled “SLG”). The 1.6 mmthick substrate had a spherical and thus complexly curved shape. Thestack was placed in a vacuum bag which was then placed in an autoclavesuch that the 0.7 mm-thick substrate was cold-formed to the 1.6 mm-thicksubstrate. The shape of the substrates and the resulting laminate weremeasured by a confocal sensor available from Micro-Epsilon used inconjunction with a general motion platform. In each instance, thesubstrate (before lamination) or laminate was placed on the generalmotion platform. The platform controls and monitors x-y position. Theconfocal sensor measures displacement of the substrate (beforelamination) or laminate from the plane of the platform. A map ofdisplacement from the platform vs. x-y position defines the shape of thesubstrate (before lamination) or laminate. FIG. 3 is a graph of themeasurement results. After lamination, both substrates had identicalshapes, demonstrating that an initially flat substrate can conform tothe shape of a thicker, more rigid substrate having a spherical shape.

Example 2

A flat substrate having length, width and thickness dimensions of 237mm×318 mm×0.7 mm including an aluminosilicate glass composition wasassembled in a stack with a complexly curved substrate. The complexlycurved substrate had the same length and width dimensions as the flatsubstrate but had a thickness of 2.1 mm and included an SLG composition.The 2.1 mm-thick substrate exhibited a center sag depth (the total depthof curvature from the edges to the center) was 6.75 mm. The stack wasplaced in a vacuum bag so the flat substrate was cold-formed to thecomplexly curved shape of the SLG substrate. The optical properties ofthe resulting laminate was measured using transmitted optics accordingto ASTM Standard C1036-06 viewing a “zebra board” through the laminateat various angles. The zebra board consisted of a series of black andwhite diagonal strips (i.e., the black stripes are 25 mm wide separatedby 25 mm wide white stripes). The quality of transmitted optics isevaluated by observing the degree of distortion of the stripes whenviewed through the laminate. The transmitted optical distortion in thecentral clear area showed no sign of degradation due to the cold-formingprocess. Small levels of distortion were detected on the periphery ofthe laminate, but were not visible to the naked eye due to thedecoration band on the periphery.

Example 3

A flat substrate having length, width and thickness dimensions of 237mm×318 mm×0.55 mm and including an aluminosilicate glass composition wasassembled with a complexly curved substrate. The complexly curvedsubstrate had the same length and width dimensions as the flat substratebut had a thickness of 1.6 mm and included a SLG composition. The 1.6mm-thick substrate exhibited a center sag depth (the total depth ofcurvature from the edges to the center) was 6.75 mm. The stack wasplaced in a vacuum bag so the flat substrate was cold-formed to thecomplexly curved shape of the SLG substrate. The optical properties ofthe resulting laminate were measured using transmitted optics in thesame manner as Example 2. The transmitted optical distortion in thecentral clear area showed no sign of degradation due to the cold-formingprocess. Small levels of distortion were detected on the periphery ofthe laminate, but were not visible to the naked eye due to thedecoration band on the periphery.

Example 4

A flat substrate having length, width and thickness dimensions of 1350mm×472 mm×0.7 mm and including an aluminosilicate glass composition wasassembled with a complexly curved substrate having the same length andwidth dimensions as the flat substrate but a thickness of 3.85 mm andincluding a SLG composition. The stack was placed in a vacuum bag so theflat substrate was cold-formed to the complexly curved shape of the SLGsubstrate. The optical properties of the resulting laminate weremeasured using transmitted optics in the same manner as Example 2. Nosign of degradation due to the cold-forming process was shown.

In a first embodiment, the disclosure provides a laminate comprising: afirst complexly-curved glass substrate having a first surface, a secondsurface opposite the first surface, and a first thickness therebetween;a second complexly-curved glass substrate having a third surface, afourth surface opposite the third surface, and a second thicknesstherebetween; and a polymer interlayer affixed to the second surface andthird surface, wherein one of the first thickness and the secondthickness is in the range of about 0.2 mm to about 0.7 mm and whereinthe third and fourth surfaces respectively have compressive stressvalues such that the fourth surface has as compressive stress value thatis greater than the compressive stress value of the third surface.

In a second embodiment, this disclosure provides the laminate of thefirst embodiment, wherein the complexly-curved glass substrate has athickness in the range of about 0.2 mm to about 0.7 mm is a chemicallystrengthened glass.

In a third embodiment, this disclosure provides the laminate of any oneor both the first embodiment and the second embodiment, wherein thefirst complexly-curved glass substrate has a thickness in the range ofabout 1.4 mm to about 3.85 mm, and the second complexly-curved glasssubstrate has a thickness in the range of about 0.2 mm to about 0.7 mm.

In a fourth embodiment, this disclosure provides the laminate of any ofthe first through third embodiments, wherein the first complexly-curvedglass substrate is made of soda lime glass.

In a fifth embodiment, this disclosure provides the laminate of any ofthe first through fourth embodiments, wherein the intervening polymerinterlayer is selected from the group consisting of polyvinyl butyral,ethylenevinylacetate, ionomers, polyvinyl chloride copolymers andthermoplastic polyurethane.

In a sixth embodiment, this disclosure provides the laminate of any ofthe first through fifth embodiments, wherein a peripheral portion of thesecond complexly-curved glass substrate exerts a compressive forceagainst the polymer interlayer, and a center portion of the secondcomplexly-curved glass substrate exerts a tensile force against thepolymer interlayer.

In a seventh embodiment, this disclosure provides the laminate of any ofthe first through sixth embodiments, further comprising a uniformdistance between the second surface and the third surface.

In an eight embodiment, this disclosure provides the laminate of any ofthe first through seventh embodiments, wherein the laminate exhibits aradii of curvature, wherein the radii of curvature are less than 1000mm.

In a ninth embodiment, this disclosure provides a vehicle comprising: abody; an opening in the body; and a laminate disposed in the opening,wherein the laminate comprises a first complexly-curved glass substratehaving a first surface, a second surface opposite the first surface, anda first thickness therebetween; a second complexly-curved glasssubstrate having a third surface, a fourth surface opposite the thirdsurface, and a second thickness therebetween; and a polymer interlayeraffixed to the second surface and third surface, wherein one of thefirst thickness and the second thickness is in the range of about 0.2 mmto about 0.7 mm and wherein the third and fourth surfaces respectivelyhave compressive stress values such that the fourth surface has ascompressive stress value that is greater than the compressive stressvalue of the third surface.

In a tenth embodiment, this disclosure provides a vehicle of the ninthembodiment wherein the laminate is moveable with respect to the opening.

In an eleventh embodiment, this disclosure provides the vehicle of anyone or both the ninth embodiment and the tenth embodiment, wherein thefirst complexly curved substrate comprises a soda lime glass compositionand a thickness of greater than about 0.7 mm and the second complexlycurved substrate comprises a strengthened glass and has a thickness inthe range from about 0.2 mm to about 0.7 mm.

In a twelfth embodiment, this disclosure provides a method of producinga complexly curved laminate, comprising: placing an interlayer between afirst complexly curved substrate and a flat second glass substrate toform a stack; applying pressure to the stack to press the second glasssubstrate against the interlayer and the first complexly curvedsubstrate to from the complexly curved laminate; and heating thecomplexly curved laminate to a temperature below 400° C.

In a thirteenth embodiment, this disclosure provides a method of thetwelfth embodiment, wherein the first complexly curved substrate is madeof metal, ceramic, plastic or glass.

In a fourteenth embodiment, this disclosure provides a method of any oneor both the twelfth and thirteenth embodiments, wherein the flat secondglass substrate comprises a thickness in the range of about 0.2 mm toabout 0.7 mm, and the first complexly curved substrate comprises athickness greater than 0.7 mm.

In a fifteenth embodiment, this disclosure provides a method of any oneof the twelfth through fourteenth embodiments, wherein the pressure isat about 1 atmosphere or greater.

In a sixteenth embodiment, this disclosure provides a method of any oneof the twelfth through fifteenth embodiments, wherein pressure isapplied to the stack using a vacuum technique.

In a seventeenth embodiment, this disclosure provides a method of anyone of the twelfth through sixteenth embodiments, wherein the pressureis applied to the stack at room temperature.

In a eighteenth embodiment, this disclosure provides a method of any oneof the twelfth through seventeenth embodiments, wherein the laminate isheated to a temperature in the range of about 100° C. to about 140° C.to form a finished bond between the bonding layer and complexly curvedglass substrates.

In a nineteenth embodiment, this disclosure provides a complexly curvedlaminate formed by the method of any one of the twelfth througheighteenth embodiments.

In twentieth embodiment, this disclosure provides a method of producinga complexly-curved laminate, comprising: forming a first glass substratehaving two major surfaces and a thickness therebetween to have acurvature along two axes and to provide a complexly curved glasssubstrate; arranging the complexly curved glass substrate with aninterlayer and a second glass substrate in a stack such that theinterlayer is between the complexly curved glass substrate and thesecond glass substrate, wherein the second glass substrate has two majorsurfaces and a thickness therebetween to have a curvature along twoaxes, wherein the curvature of the second glass substrate does not matchthe curvature of the first glass substrate; and applying pressure to thestack at room temperature, wherein the curvature of the second glasssubstrate conforms to the curvature of the first glass substrate to forma complexly curved laminate.

In a twenty-first embodiment, this disclosure provides a method of thetwentieth embodiment, which further comprises heating stack to atemperature in the range of about 100° C. to about 140° C. to form abond between the interlayer and the first and second glass substrates.

In a twenty-second embodiment, this disclosure provides a method of anyone or both the twentieth and twenty-first embodiment, wherein thesecond glass substrate is a chemically strengthened glass having athickness in the range of about 0.2 mm to about 0.7 mm, and the firstglass substrate is a soda lime glass having a thickness in the range ofabout 1.4 mm to about 3.85 mm.

In a twenty-third embodiment, this disclosure provides a complexlycurved laminate formed by the method of any one of the twentieth throughtwenty-second embodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A laminated article comprising: a first substratecomprising a first curved surface and a complexly-curved shape; a glasssubstrate comprising a second surface and a third surface opposite thesecond surface; and at least one of a polymer interlayer and an adhesiveaffixed to the first curved surface and the second surface, wherein afirst compressive stress value of the second surface differs from asecond compressive stress value of the third surface as a result of theglass substrate being cold-formed against the first curved surface. 2.The laminated article of claim 1, wherein only the adhesive is affixedto the first curved surface and the second surface.
 3. The laminatedarticle of claim 2, further comprising a decoration band disposed at aperiphery of at least one of the first substrate and the glasssubstrate.
 4. The laminated article of claim 1, wherein the firstsubstrate comprises a greater rigidity than the glass substrate.
 5. Thelaminated article of claim 1, wherein glass substrate comprises athickness extending between the second surface and the third surfacethat is greater than or equal to 0.2 and less than or equal to 1.4. 6.The laminated article of claim 5: wherein first substrate is formed of aglass, and a thickness of the first substrate is less than or equal to4.0 mm.
 7. The laminated article of claim 6, wherein: only the polymerinterlayer is affixed to the first curved surface and the secondsurface, and the polymer interlayer comprises polyvinyl butyral,ethylenevinylacetate, an ionomer, a polyvinyl chloride copolymer, or athermoplastic polyurethane.
 8. The laminated article of claim 6, whereinthe laminated article comprises a windshield, a backlight, a sunroof, afix-mounted roof panel, or a sidelight.
 9. The laminated article ofclaim 8, wherein the first substrate is constructed of a soda limeglass, an alkali aluminosilicate glass, an alkali-containingborosilicate glass, or an alkali aluminoborosilicate glass.
 10. Thelaminated article of claim 9, wherein the glass substrate comprises adifferent composition than the glass of the first substrate.
 11. Thelaminated article of claim 10, wherein the second substrate ischemically strengthened and comprises a thickness that is less than halfof the thickness of the first substrate.
 12. The laminated article ofclaim 1, wherein a peripheral portion of the glass substrate exerts acompressive force against the polymer interlayer, and a center portionof the glass substrate exerts a tensile force against the polymerinterlayer.
 13. The laminated article of claim 1, wherein the firstcurved surface and the second surface are separated by a uniformdistance.
 14. The laminated article of claim 1, wherein thecomplexly-curved shape comprises a first radius of curvature of 5 m orless along a first axis and second radius of curvature of 5 m or lessalong a second axis extending in a different direction than the firstaxis.
 15. The laminated article of claim 14, wherein the first axis isperpendicular to the second axis.
 16. The laminated article of claim 14,wherein the first axis is not perpendicular to the second axis.
 17. Thelaminated article of claim 14, wherein the first radius of curvature isgreater than or equal to 4.0 m and less than or equal to 5.0 m and thesecond radius of curvature is greater than or equal to 2.0 m and lessthan or equal to 2.5 M.
 18. The laminated article of claim 1, whereinthe laminate comprises a length that is greater than or equal to 30.5 cmand less than or equal to 127 cm and a width that is greater than orequal to 30.5 cm and less than or equal to 183 cm.